Today, a mobile device connected to an IP Multimedia Subsystem (IMS) cannot operate in another IP Multimedia Subsystem. If the mobile device moves from one IMS to another IMS, parameters assigned to the mobile device from the first IMS are lost in the second IMS. These parameters can include subscriber-specific features such as the type of service, the level of services, and the quality of service.
An adhoc solution has been created that duplicates subscriber-specific features in each IMS. Therefore, when the mobile device moves from one IMS to another IMS, the desired features will be available. However, this arrangement is quite expensive as it requires duplication of resources across multiple networks.
A solution is needed that would define new functions within an IMS that would allow it to communicate with another IMS network. The solution needs to allow a mobile device to access offered features but minimize duplication of resources.